Deterministic Finite Automata

In order to describe a Deterministic Finite Automation, $\boxed{\text{DFA}}$, we describe 5 things:

• its states
• its input alphabet
• its (unique) initial state
• its favourable (or accepting) states there can be none, or more than one
• its transition function: for every (state, input symbol) pair we have to tell what the next state should be

A word $w$ is accepted by DFA $A$ if the computation of $A$ on input $w$ ends up in some favourable state. Otherwise, $w$ is rejected by $A$.